The set-up 
==========

I set up a Pi Zero running Stretch Lite, and connected it via USB in OTG mode to a MacBook.

I successfully found it at ``raspberrypi.local`` from the Macintosh, was able to ssh in, install various packages and run a small Python application.

The problem
===========

While the application was running, it seems to have dropped off the network with a ``broken pipe``:

    pi@raspberrypi:~ $ packet_write_wait: Connection to fe80::a648:c9cc:e29b:761e%bridge100 port 22: Broken pipe

Sequence of events
==================

* MacBook: Internet Sharing was *on* (as it has been for weeks).
* Pi SD card was configured appropriately.
* I connected the Pi via USB to the MacBook.
* I immediately was able to ``ssh [email protected]``.
* I don't know what IP address the Pi had (I think the Mac gave it a 192.168.2.x address), but it was able to reach the Internet.
* While on the Pi, I installed various packages using apt and pip.
* I connected the servos and started using my Python application I downloaded from GitHub.
* While executing the program, which was producing output in the terminal, the Pi appeared to lose all network connectivity to the MacBook.
* The Pi continued for several minutes more until the program finished running.
* While trying to reconnect, I could no longer resolve ``raspberrypi.local`` from the Macintosh. 
* The output of ``arp -a`` showed no sign of it:

        ➜  ~ arp -a   
         dsldevice.lan (192.168.1.1) at c4:ea:1d:6c:bd:ae on en0 ifscope [ethernet]
         danieles-mbp.lan (192.168.1.137) at b8:e8:56:34:97:12 on en0 ifscope permanent [ethernet]
         ? (192.168.1.255) at ff:ff:ff:ff:ff:ff on en0 ifscope [ethernet]
         ? (224.0.0.251) at 1:0:5e:0:0:fb on en0 ifscope permanent [ethernet]
         ? (224.6.7.8) at 1:0:5e:6:7:8 on en0 ifscope permanent [ethernet]
         ? (239.255.255.250) at 1:0:5e:7f:ff:fa on en0 ifscope permanent [ethernet]
         broadcasthost (255.255.255.255) at ff:ff:ff:ff:ff:ff on en0 ifscope [ethernet]

* After rebooting the Pi by disconnecting the power, I was once again able to reach it at ``raspberrypi.local``.
* However, the Pi now has a 169.254.x.x address and cannot resolve host names, nor can it reach remote IP addresses.
* The Macintosh Network system preferences shows an *RNDIS/Ethernet gadget* attached, on a 169.254.x.x (not the one of the Pi - this is the address of that interface of the Mac).